Linux-2.6.12-rc2v2.6.12-rc2

Initial git repository build. I'm not bothering with the full history,
even though we have it. We can create a separate "historical" git
archive of that later if we want to, and in the meantime it's about
3.2GB when imported into git - space that would just make the early
git days unnecessarily complicated, when we don't have a lot of good
infrastructure for it.

Let it rip!

1 files changed, 788 insertions, 0 deletions

diff --git a/fs/befs/btree.c b/fs/befs/btree.c
new file mode 100644
index 000000000000..76e219799409
--- /dev/null
+++ b/fs/befs/btree.c
@@ -0,0 +1,788 @@
+/*
+ * linux/fs/befs/btree.c
+ *
+ * Copyright (C) 2001-2002 Will Dyson <will_dyson@pobox.com>
+ *
+ * Licensed under the GNU GPL. See the file COPYING for details.
+ *
+ * 2002-02-05: Sergey S. Kostyliov added binary search withing
+ *              btree nodes.
+ *
+ * Many thanks to:
+ *
+ * Dominic Giampaolo, author of "Practical File System
+ * Design with the Be File System", for such a helpful book.
+ * 
+ * Marcus J. Ranum, author of the b+tree package in 
+ * comp.sources.misc volume 10. This code is not copied from that
+ * work, but it is partially based on it.
+ *
+ * Makoto Kato, author of the original BeFS for linux filesystem
+ * driver.
+ */
+
+#include <linux/kernel.h>
+#include <linux/string.h>
+#include <linux/slab.h>
+#include <linux/mm.h>
+#include <linux/buffer_head.h>
+
+#include "befs.h"
+#include "btree.h"
+#include "datastream.h"
+#include "endian.h"
+
+/*
+ * The btree functions in this file are built on top of the
+ * datastream.c interface, which is in turn built on top of the
+ * io.c interface.
+ */
+
+/* Befs B+tree structure:
+ * 
+ * The first thing in the tree is the tree superblock. It tells you
+ * all kinds of useful things about the tree, like where the rootnode
+ * is located, and the size of the nodes (always 1024 with current version
+ * of BeOS).
+ *
+ * The rest of the tree consists of a series of nodes. Nodes contain a header
+ * (struct befs_btree_nodehead), the packed key data, an array of shorts 
+ * containing the ending offsets for each of the keys, and an array of
+ * befs_off_t values. In interior nodes, the keys are the ending keys for 
+ * the childnode they point to, and the values are offsets into the 
+ * datastream containing the tree. 
+ */
+
+/* Note:
+ * 
+ * The book states 2 confusing things about befs b+trees. First, 
+ * it states that the overflow field of node headers is used by internal nodes
+ * to point to another node that "effectively continues this one". Here is what
+ * I believe that means. Each key in internal nodes points to another node that
+ * contains key values less than itself. Inspection reveals that the last key 
+ * in the internal node is not the last key in the index. Keys that are 
+ * greater than the last key in the internal node go into the overflow node. 
+ * I imagine there is a performance reason for this.
+ *
+ * Second, it states that the header of a btree node is sufficient to 
+ * distinguish internal nodes from leaf nodes. Without saying exactly how. 
+ * After figuring out the first, it becomes obvious that internal nodes have
+ * overflow nodes and leafnodes do not.
+ */
+
+/* 
+ * Currently, this code is only good for directory B+trees.
+ * In order to be used for other BFS indexes, it needs to be extended to handle
+ * duplicate keys and non-string keytypes (int32, int64, float, double).
+ */
+
+/*
+ * In memory structure of each btree node
+ */
+typedef struct {
+        befs_btree_nodehead head;       /* head of node converted to cpu byteorder */
+        struct buffer_head *bh;
+        befs_btree_nodehead *od_node;   /* on disk node */
+} befs_btree_node;
+
+/* local constants */
+static const befs_off_t befs_bt_inval = 0xffffffffffffffffULL;
+
+/* local functions */
+static int befs_btree_seekleaf(struct super_block *sb, befs_data_stream * ds,
+                               befs_btree_super * bt_super,
+                               befs_btree_node * this_node,
+                               befs_off_t * node_off);
+
+static int befs_bt_read_super(struct super_block *sb, befs_data_stream * ds,
+                              befs_btree_super * sup);
+
+static int befs_bt_read_node(struct super_block *sb, befs_data_stream * ds,
+                             befs_btree_node * node, befs_off_t node_off);
+
+static int befs_leafnode(befs_btree_node * node);
+
+static u16 *befs_bt_keylen_index(befs_btree_node * node);
+
+static befs_off_t *befs_bt_valarray(befs_btree_node * node);
+
+static char *befs_bt_keydata(befs_btree_node * node);
+
+static int befs_find_key(struct super_block *sb, befs_btree_node * node,
+                         const char *findkey, befs_off_t * value);
+
+static char *befs_bt_get_key(struct super_block *sb, befs_btree_node * node,
+                             int index, u16 * keylen);
+
+static int befs_compare_strings(const void *key1, int keylen1,
+                                const void *key2, int keylen2);
+
+/**
+ * befs_bt_read_super - read in btree superblock convert to cpu byteorder
+ * @sb: Filesystem superblock
+ * @ds: Datastream to read from
+ * @sup: Buffer in which to place the btree superblock
+ *
+ * Calls befs_read_datastream to read in the btree superblock and
+ * makes sure it is in cpu byteorder, byteswapping if necessary.
+ *
+ * On success, returns BEFS_OK and *@sup contains the btree superblock,
+ * in cpu byte order.
+ *
+ * On failure, BEFS_ERR is returned.
+ */
+static int
+befs_bt_read_super(struct super_block *sb, befs_data_stream * ds,
+                   befs_btree_super * sup)
+{
+        struct buffer_head *bh = NULL;
+        befs_btree_super *od_sup = NULL;
+
+        befs_debug(sb, "---> befs_btree_read_super()");
+
+        bh = befs_read_datastream(sb, ds, 0, NULL);
+
+        if (!bh) {
+                befs_error(sb, "Couldn't read index header.");
+                goto error;
+        }
+        od_sup = (befs_btree_super *) bh->b_data;
+        befs_dump_index_entry(sb, od_sup);
+
+        sup->magic = fs32_to_cpu(sb, od_sup->magic);
+        sup->node_size = fs32_to_cpu(sb, od_sup->node_size);
+        sup->max_depth = fs32_to_cpu(sb, od_sup->max_depth);
+        sup->data_type = fs32_to_cpu(sb, od_sup->data_type);
+        sup->root_node_ptr = fs64_to_cpu(sb, od_sup->root_node_ptr);
+        sup->free_node_ptr = fs64_to_cpu(sb, od_sup->free_node_ptr);
+        sup->max_size = fs64_to_cpu(sb, od_sup->max_size);
+
+        brelse(bh);
+        if (sup->magic != BEFS_BTREE_MAGIC) {
+                befs_error(sb, "Index header has bad magic.");
+                goto error;
+        }
+
+        befs_debug(sb, "<--- befs_btree_read_super()");
+        return BEFS_OK;
+
+      error:
+        befs_debug(sb, "<--- befs_btree_read_super() ERROR");
+        return BEFS_ERR;
+}
+
+/**
+ * befs_bt_read_node - read in btree node and convert to cpu byteorder
+ * @sb: Filesystem superblock
+ * @ds: Datastream to read from
+ * @node: Buffer in which to place the btree node
+ * @node_off: Starting offset (in bytes) of the node in @ds
+ *
+ * Calls befs_read_datastream to read in the indicated btree node and
+ * makes sure its header fields are in cpu byteorder, byteswapping if
+ * necessary.
+ * Note: node->bh must be NULL when this function called first
+ * time. Don't forget brelse(node->bh) after last call.
+ *
+ * On success, returns BEFS_OK and *@node contains the btree node that
+ * starts at @node_off, with the node->head fields in cpu byte order.
+ *
+ * On failure, BEFS_ERR is returned.
+ */
+
+static int
+befs_bt_read_node(struct super_block *sb, befs_data_stream * ds,
+                  befs_btree_node * node, befs_off_t node_off)
+{
+        uint off = 0;
+
+        befs_debug(sb, "---> befs_bt_read_node()");
+
+        if (node->bh)
+                brelse(node->bh);
+
+        node->bh = befs_read_datastream(sb, ds, node_off, &off);
+        if (!node->bh) {
+                befs_error(sb, "befs_bt_read_node() failed to read "
+                           "node at %Lu", node_off);
+                befs_debug(sb, "<--- befs_bt_read_node() ERROR");
+
+                return BEFS_ERR;
+        }
+        node->od_node =
+            (befs_btree_nodehead *) ((void *) node->bh->b_data + off);
+
+        befs_dump_index_node(sb, node->od_node);
+
+        node->head.left = fs64_to_cpu(sb, node->od_node->left);
+        node->head.right = fs64_to_cpu(sb, node->od_node->right);
+        node->head.overflow = fs64_to_cpu(sb, node->od_node->overflow);
+        node->head.all_key_count =
+            fs16_to_cpu(sb, node->od_node->all_key_count);
+        node->head.all_key_length =
+            fs16_to_cpu(sb, node->od_node->all_key_length);
+
+        befs_debug(sb, "<--- befs_btree_read_node()");
+        return BEFS_OK;
+}
+
+/**
+ * befs_btree_find - Find a key in a befs B+tree
+ * @sb: Filesystem superblock
+ * @ds: Datastream containing btree
+ * @key: Key string to lookup in btree
+ * @value: Value stored with @key
+ *
+ * On sucess, returns BEFS_OK and sets *@value to the value stored
+ * with @key (usually the disk block number of an inode).
+ *
+ * On failure, returns BEFS_ERR or BEFS_BT_NOT_FOUND.
+ * 
+ * Algorithm: 
+ *   Read the superblock and rootnode of the b+tree.
+ *   Drill down through the interior nodes using befs_find_key().
+ *   Once at the correct leaf node, use befs_find_key() again to get the
+ *   actuall value stored with the key.
+ */
+int
+befs_btree_find(struct super_block *sb, befs_data_stream * ds,
+                const char *key, befs_off_t * value)
+{
+        befs_btree_node *this_node = NULL;
+        befs_btree_super bt_super;
+        befs_off_t node_off;
+        int res;
+
+        befs_debug(sb, "---> befs_btree_find() Key: %s", key);
+
+        if (befs_bt_read_super(sb, ds, &bt_super) != BEFS_OK) {
+                befs_error(sb,
+                           "befs_btree_find() failed to read index superblock");
+                goto error;
+        }
+
+        this_node = (befs_btree_node *) kmalloc(sizeof (befs_btree_node),
+                                                GFP_NOFS);
+        if (!this_node) {
+                befs_error(sb, "befs_btree_find() failed to allocate %u "
+                           "bytes of memory", sizeof (befs_btree_node));
+                goto error;
+        }
+
+        this_node->bh = NULL;
+
+        /* read in root node */
+        node_off = bt_super.root_node_ptr;
+        if (befs_bt_read_node(sb, ds, this_node, node_off) != BEFS_OK) {
+                befs_error(sb, "befs_btree_find() failed to read "
+                           "node at %Lu", node_off);
+                goto error_alloc;
+        }
+
+        while (!befs_leafnode(this_node)) {
+                res = befs_find_key(sb, this_node, key, &node_off);
+                if (res == BEFS_BT_NOT_FOUND)
+                        node_off = this_node->head.overflow;
+                /* if no match, go to overflow node */
+                if (befs_bt_read_node(sb, ds, this_node, node_off) != BEFS_OK) {
+                        befs_error(sb, "befs_btree_find() failed to read "
+                                   "node at %Lu", node_off);
+                        goto error_alloc;
+                }
+        }
+
+        /* at the correct leaf node now */
+
+        res = befs_find_key(sb, this_node, key, value);
+
+        brelse(this_node->bh);
+        kfree(this_node);
+
+        if (res != BEFS_BT_MATCH) {
+                befs_debug(sb, "<--- befs_btree_find() Key %s not found", key);
+                *value = 0;
+                return BEFS_BT_NOT_FOUND;
+        }
+        befs_debug(sb, "<--- befs_btree_find() Found key %s, value %Lu",
+                   key, *value);
+        return BEFS_OK;
+
+      error_alloc:
+        kfree(this_node);
+      error:
+        *value = 0;
+        befs_debug(sb, "<--- befs_btree_find() ERROR");
+        return BEFS_ERR;
+}
+
+/**
+ * befs_find_key - Search for a key within a node
+ * @sb: Filesystem superblock
+ * @node: Node to find the key within
+ * @key: Keystring to search for
+ * @value: If key is found, the value stored with the key is put here
+ *
+ * finds exact match if one exists, and returns BEFS_BT_MATCH
+ * If no exact match, finds first key in node that is greater
+ * (alphabetically) than the search key and returns BEFS_BT_PARMATCH
+ * (for partial match, I guess). Can you think of something better to
+ * call it?
+ *
+ * If no key was a match or greater than the search key, return
+ * BEFS_BT_NOT_FOUND.
+ *
+ * Use binary search instead of a linear.
+ */
+static int
+befs_find_key(struct super_block *sb, befs_btree_node * node,
+              const char *findkey, befs_off_t * value)
+{
+        int first, last, mid;
+        int eq;
+        u16 keylen;
+        int findkey_len;
+        char *thiskey;
+        befs_off_t *valarray;
+
+        befs_debug(sb, "---> befs_find_key() %s", findkey);
+
+        *value = 0;
+
+        findkey_len = strlen(findkey);
+
+        /* if node can not contain key, just skeep this node */
+        last = node->head.all_key_count - 1;
+        thiskey = befs_bt_get_key(sb, node, last, &keylen);
+
+        eq = befs_compare_strings(thiskey, keylen, findkey, findkey_len);
+        if (eq < 0) {
+                befs_debug(sb, "<--- befs_find_key() %s not found", findkey);
+                return BEFS_BT_NOT_FOUND;
+        }
+
+        valarray = befs_bt_valarray(node);
+
+        /* simple binary search */
+        first = 0;
+        mid = 0;
+        while (last >= first) {
+                mid = (last + first) / 2;
+                befs_debug(sb, "first: %d, last: %d, mid: %d", first, last,
+                           mid);
+                thiskey = befs_bt_get_key(sb, node, mid, &keylen);
+                eq = befs_compare_strings(thiskey, keylen, findkey,
+                                          findkey_len);
+
+                if (eq == 0) {
+                        befs_debug(sb, "<--- befs_find_key() found %s at %d",
+                                   thiskey, mid);
+
+                        *value = fs64_to_cpu(sb, valarray[mid]);
+                        return BEFS_BT_MATCH;
+                }
+                if (eq > 0)
+                        last = mid - 1;
+                else
+                        first = mid + 1;
+        }
+        if (eq < 0)
+                *value = fs64_to_cpu(sb, valarray[mid + 1]);
+        else
+                *value = fs64_to_cpu(sb, valarray[mid]);
+        befs_debug(sb, "<--- befs_find_key() found %s at %d", thiskey, mid);
+        return BEFS_BT_PARMATCH;
+}
+
+/**
+ * befs_btree_read - Traverse leafnodes of a btree
+ * @sb: Filesystem superblock
+ * @ds: Datastream containing btree
+ * @key_no: Key number (alphabetical order) of key to read
+ * @bufsize: Size of the buffer to return key in
+ * @keybuf: Pointer to a buffer to put the key in
+ * @keysize: Length of the returned key
+ * @value: Value stored with the returned key
+ *
+ * Heres how it works: Key_no is the index of the key/value pair to 
+ * return in keybuf/value.
+ * Bufsize is the size of keybuf (BEFS_NAME_LEN+1 is a good size). Keysize is 
+ * the number of charecters in the key (just a convenience).
+ *
+ * Algorithm:
+ *   Get the first leafnode of the tree. See if the requested key is in that
+ *   node. If not, follow the node->right link to the next leafnode. Repeat 
+ *   until the (key_no)th key is found or the tree is out of keys.
+ */
+int
+befs_btree_read(struct super_block *sb, befs_data_stream * ds,
+                loff_t key_no, size_t bufsize, char *keybuf, size_t * keysize,
+                befs_off_t * value)
+{
+        befs_btree_node *this_node;
+        befs_btree_super bt_super;
+        befs_off_t node_off = 0;
+        int cur_key;
+        befs_off_t *valarray;
+        char *keystart;
+        u16 keylen;
+        int res;
+
+        uint key_sum = 0;
+
+        befs_debug(sb, "---> befs_btree_read()");
+
+        if (befs_bt_read_super(sb, ds, &bt_super) != BEFS_OK) {
+                befs_error(sb,
+                           "befs_btree_read() failed to read index superblock");
+                goto error;
+        }
+
+        if ((this_node = (befs_btree_node *)
+             kmalloc(sizeof (befs_btree_node), GFP_NOFS)) == NULL) {
+                befs_error(sb, "befs_btree_read() failed to allocate %u "
+                           "bytes of memory", sizeof (befs_btree_node));
+                goto error;
+        }
+
+        node_off = bt_super.root_node_ptr;
+        this_node->bh = NULL;
+
+        /* seeks down to first leafnode, reads it into this_node */
+        res = befs_btree_seekleaf(sb, ds, &bt_super, this_node, &node_off);
+        if (res == BEFS_BT_EMPTY) {
+                brelse(this_node->bh);
+                kfree(this_node);
+                *value = 0;
+                *keysize = 0;
+                befs_debug(sb, "<--- befs_btree_read() Tree is EMPTY");
+                return BEFS_BT_EMPTY;
+        } else if (res == BEFS_ERR) {
+                goto error_alloc;
+        }
+
+        /* find the leaf node containing the key_no key */
+
+        while (key_sum + this_node->head.all_key_count <= key_no) {
+
+                /* no more nodes to look in: key_no is too large */
+                if (this_node->head.right == befs_bt_inval) {
+                        *keysize = 0;
+                        *value = 0;
+                        befs_debug(sb,
+                                   "<--- befs_btree_read() END of keys at %Lu",
+                                   key_sum + this_node->head.all_key_count);
+                        brelse(this_node->bh);
+                        kfree(this_node);
+                        return BEFS_BT_END;
+                }
+
+                key_sum += this_node->head.all_key_count;
+                node_off = this_node->head.right;
+
+                if (befs_bt_read_node(sb, ds, this_node, node_off) != BEFS_OK) {
+                        befs_error(sb, "befs_btree_read() failed to read "
+                                   "node at %Lu", node_off);
+                        goto error_alloc;
+                }
+        }
+
+        /* how many keys into this_node is key_no */
+        cur_key = key_no - key_sum;
+
+        /* get pointers to datastructures within the node body */
+        valarray = befs_bt_valarray(this_node);
+
+        keystart = befs_bt_get_key(sb, this_node, cur_key, &keylen);
+
+        befs_debug(sb, "Read [%Lu,%d]: keysize %d", node_off, cur_key, keylen);
+
+        if (bufsize < keylen + 1) {
+                befs_error(sb, "befs_btree_read() keybuf too small (%u) "
+                           "for key of size %d", bufsize, keylen);
+                brelse(this_node->bh);
+                goto error_alloc;
+        };
+
+        strncpy(keybuf, keystart, keylen);
+        *value = fs64_to_cpu(sb, valarray[cur_key]);
+        *keysize = keylen;
+        keybuf[keylen] = '\0';
+
+        befs_debug(sb, "Read [%Lu,%d]: Key \"%.*s\", Value %Lu", node_off,
+                   cur_key, keylen, keybuf, *value);
+
+        brelse(this_node->bh);
+        kfree(this_node);
+
+        befs_debug(sb, "<--- befs_btree_read()");
+
+        return BEFS_OK;
+
+      error_alloc:
+        kfree(this_node);
+
+      error:
+        *keysize = 0;
+        *value = 0;
+        befs_debug(sb, "<--- befs_btree_read() ERROR");
+        return BEFS_ERR;
+}
+
+/**
+ * befs_btree_seekleaf - Find the first leafnode in the btree
+ * @sb: Filesystem superblock
+ * @ds: Datastream containing btree
+ * @bt_super: Pointer to the superblock of the btree
+ * @this_node: Buffer to return the leafnode in
+ * @node_off: Pointer to offset of current node within datastream. Modified
+ *              by the function.
+ *
+ *
+ * Helper function for btree traverse. Moves the current position to the 
+ * start of the first leaf node.
+ *
+ * Also checks for an empty tree. If there are no keys, returns BEFS_BT_EMPTY.
+ */
+static int
+befs_btree_seekleaf(struct super_block *sb, befs_data_stream * ds,
+                    befs_btree_super * bt_super, befs_btree_node * this_node,
+                    befs_off_t * node_off)
+{
+
+        befs_debug(sb, "---> befs_btree_seekleaf()");
+
+        if (befs_bt_read_node(sb, ds, this_node, *node_off) != BEFS_OK) {
+                befs_error(sb, "befs_btree_seekleaf() failed to read "
+                           "node at %Lu", *node_off);
+                goto error;
+        }
+        befs_debug(sb, "Seekleaf to root node %Lu", *node_off);
+
+        if (this_node->head.all_key_count == 0 && befs_leafnode(this_node)) {
+                befs_debug(sb, "<--- befs_btree_seekleaf() Tree is EMPTY");
+                return BEFS_BT_EMPTY;
+        }
+
+        while (!befs_leafnode(this_node)) {
+
+                if (this_node->head.all_key_count == 0) {
+                        befs_debug(sb, "befs_btree_seekleaf() encountered "
+                                   "an empty interior node: %Lu. Using Overflow "
+                                   "node: %Lu", *node_off,
+                                   this_node->head.overflow);
+                        *node_off = this_node->head.overflow;
+                } else {
+                        befs_off_t *valarray = befs_bt_valarray(this_node);
+                        *node_off = fs64_to_cpu(sb, valarray[0]);
+                }
+                if (befs_bt_read_node(sb, ds, this_node, *node_off) != BEFS_OK) {
+                        befs_error(sb, "befs_btree_seekleaf() failed to read "
+                                   "node at %Lu", *node_off);
+                        goto error;
+                }
+
+                befs_debug(sb, "Seekleaf to child node %Lu", *node_off);
+        }
+        befs_debug(sb, "Node %Lu is a leaf node", *node_off);
+
+        return BEFS_OK;
+
+      error:
+        befs_debug(sb, "<--- befs_btree_seekleaf() ERROR");
+        return BEFS_ERR;
+}
+
+/**
+ * befs_leafnode - Determine if the btree node is a leaf node or an 
+ * interior node
+ * @node: Pointer to node structure to test
+ * 
+ * Return 1 if leaf, 0 if interior
+ */
+static int
+befs_leafnode(befs_btree_node * node)
+{
+        /* all interior nodes (and only interior nodes) have an overflow node */
+        if (node->head.overflow == befs_bt_inval)
+                return 1;
+        else
+                return 0;
+}
+
+/**
+ * befs_bt_keylen_index - Finds start of keylen index in a node
+ * @node: Pointer to the node structure to find the keylen index within
+ *
+ * Returns a pointer to the start of the key length index array
+ * of the B+tree node *@node
+ *
+ * "The length of all the keys in the node is added to the size of the
+ * header and then rounded up to a multiple of four to get the beginning
+ * of the key length index" (p.88, practical filesystem design).
+ *
+ * Except that rounding up to 8 works, and rounding up to 4 doesn't.
+ */
+static u16 *
+befs_bt_keylen_index(befs_btree_node * node)
+{
+        const int keylen_align = 8;
+        unsigned long int off =
+            (sizeof (befs_btree_nodehead) + node->head.all_key_length);
+        ulong tmp = off % keylen_align;
+
+        if (tmp)
+                off += keylen_align - tmp;
+
+        return (u16 *) ((void *) node->od_node + off);
+}
+
+/**
+ * befs_bt_valarray - Finds the start of value array in a node
+ * @node: Pointer to the node structure to find the value array within
+ *
+ * Returns a pointer to the start of the value array
+ * of the node pointed to by the node header
+ */
+static befs_off_t *
+befs_bt_valarray(befs_btree_node * node)
+{
+        void *keylen_index_start = (void *) befs_bt_keylen_index(node);
+        size_t keylen_index_size = node->head.all_key_count * sizeof (u16);
+
+        return (befs_off_t *) (keylen_index_start + keylen_index_size);
+}
+
+/**
+ * befs_bt_keydata - Finds start of keydata array in a node
+ * @node: Pointer to the node structure to find the keydata array within
+ *
+ * Returns a pointer to the start of the keydata array
+ * of the node pointed to by the node header 
+ */
+static char *
+befs_bt_keydata(befs_btree_node * node)
+{
+        return (char *) ((void *) node->od_node + sizeof (befs_btree_nodehead));
+}
+
+/**
+ * befs_bt_get_key - returns a pointer to the start of a key
+ * @sb: filesystem superblock
+ * @node: node in which to look for the key
+ * @index: the index of the key to get
+ * @keylen: modified to be the length of the key at @index
+ *
+ * Returns a valid pointer into @node on success.
+ * Returns NULL on failure (bad input) and sets *@keylen = 0
+ */
+static char *
+befs_bt_get_key(struct super_block *sb, befs_btree_node * node,
+                int index, u16 * keylen)
+{
+        int prev_key_end;
+        char *keystart;
+        u16 *keylen_index;
+
+        if (index < 0 || index > node->head.all_key_count) {
+                *keylen = 0;
+                return NULL;
+        }
+
+        keystart = befs_bt_keydata(node);
+        keylen_index = befs_bt_keylen_index(node);
+
+        if (index == 0)
+                prev_key_end = 0;
+        else
+                prev_key_end = fs16_to_cpu(sb, keylen_index[index - 1]);
+
+        *keylen = fs16_to_cpu(sb, keylen_index[index]) - prev_key_end;
+
+        return keystart + prev_key_end;
+}
+
+/**
+ * befs_compare_strings - compare two strings
+ * @key1: pointer to the first key to be compared 
+ * @keylen1: length in bytes of key1
+ * @key2: pointer to the second key to be compared
+ * @kelen2: length in bytes of key2
+ *
+ * Returns 0 if @key1 and @key2 are equal.
+ * Returns >0 if @key1 is greater.
+ * Returns <0 if @key2 is greater..
+ */
+static int
+befs_compare_strings(const void *key1, int keylen1,
+                     const void *key2, int keylen2)
+{
+        int len = min_t(int, keylen1, keylen2);
+        int result = strncmp(key1, key2, len);
+        if (result == 0)
+                result = keylen1 - keylen2;
+        return result;
+}
+
+/* These will be used for non-string keyed btrees */
+#if 0
+static int
+btree_compare_int32(cont void *key1, int keylen1, const void *key2, int keylen2)
+{
+        return *(int32_t *) key1 - *(int32_t *) key2;
+}
+
+static int
+btree_compare_uint32(cont void *key1, int keylen1,
+                     const void *key2, int keylen2)
+{
+        if (*(u_int32_t *) key1 == *(u_int32_t *) key2)
+                return 0;
+        else if (*(u_int32_t *) key1 > *(u_int32_t *) key2)
+                return 1;
+
+        return -1;
+}
+static int
+btree_compare_int64(cont void *key1, int keylen1, const void *key2, int keylen2)
+{
+        if (*(int64_t *) key1 == *(int64_t *) key2)
+                return 0;
+        else if (*(int64_t *) key1 > *(int64_t *) key2)
+                return 1;
+
+        return -1;
+}
+
+static int
+btree_compare_uint64(cont void *key1, int keylen1,
+                     const void *key2, int keylen2)
+{
+        if (*(u_int64_t *) key1 == *(u_int64_t *) key2)
+                return 0;
+        else if (*(u_int64_t *) key1 > *(u_int64_t *) key2)
+                return 1;
+
+        return -1;
+}
+
+static int
+btree_compare_float(cont void *key1, int keylen1, const void *key2, int keylen2)
+{
+        float result = *(float *) key1 - *(float *) key2;
+        if (result == 0.0f)
+                return 0;
+
+        return (result < 0.0f) ? -1 : 1;
+}
+
+static int
+btree_compare_double(cont void *key1, int keylen1,
+                     const void *key2, int keylen2)
+{
+        double result = *(double *) key1 - *(double *) key2;
+        if (result == 0.0)
+                return 0;
+
+        return (result < 0.0) ? -1 : 1;
+}
+#endif                          //0